To identify the modified tyrosine residue in DNase in which the molecule has been iodinated by using lactoperoxidase system. This will be carried out by using radio autogram of the peptide map of modified DNase with radioactive iodine to locate iodine containing peptide. To identify the modified residue caused by the treatment of DNase with 2-nitro-5-thiocyanobenzoic acid (NTCB). This will be accomplished by using radio actively labelled NTCB and checking the absorption spectrum of the modified protein, and also to explain why there are cleavages of some peptide bonds during NTCB treatment. Chemistry of the entire reaction will be studied. To study the primary structure of malt DNase as compared to that of pancreatic DNase. This will include peptide mapping, positioning of disulfide bridges, methione residues, carbohydrate side chain, and tryptophan residues, NH2- and COOH-terminal residues as well as essential histidine and tyrosine residues. To further purify ovine DNase. This will require affinity elution of DNase on DEAE-cellulose columns with and without Ca2 ion present. Also to characterize the multiple forms of ovine DNase. This will give some insights as to how protein sequences were evolved in cow and sheep and answer questions about the biological importance of sialic acid which is attached to some of the forms of DNase.